Guide catheters for accessing cardiac sites

ABSTRACT

Guide catheters for facilitating implantation of cardiac leads for applying electrical stimulation to and/or sensing electrical activity of the heart through one or more electrodes positioned at an implantation site within a heart chamber or cardiac vessel adjacent a heart chamber. Such a cardiac lead has low torqueability and pushability through a pathway to enable attachment of the cardiac lead at the implantation site. The catheter body comprises a delivery lumen to introduce a small diameter cardiac lead and a guide lumen to receive a guide tool to locate the catheter body distal end at the implantation site. The small diameter lumen within a small diameter guide tube extends distally from the delivery exit port of the delivery lumen. The catheter body is shaped to bias the delivery lumen exit port toward the heart.

TECHNICAL FIELD

The present invention relates to bilumen guide catheters forintroduction and implantation of cardiac leads for applying electricalstimulation to and/or sensing electrical activity of the heart or theintroduction of other medical instruments and materials into cardiacvessels, particularly the coronary sinus (CS) and vessels branchingtherefrom.

BACKGROUND

Implantable permanent and temporary medical electrical stimulationand/or sensing leads are well known in the fields of cardiac stimulationand monitoring, including cardiac pacing andcardioversion/defibrillation, and in other fields of electricalstimulation or monitoring of electrical signals or other physiologicparameters. In the field of cardiac stimulation and monitoring, theelectrodes of epicardial or endocardial cardiac leads are affixedagainst the epicardium or endocardium, respectively, or insertedtherethrough into the underlying myocardium of the heart wall.

It has become possible to reduce endocardial lead body diameters from 10to 12 French (3.3 to 4.0 mm) down to 2 French (0.66 mm) presentlythrough a variety of improvements in conductor and insulator materialsand manufacturing techniques. The lead bodies of such small diameter, 2French, endocardial leads are formed without a lumen that accommodatesuse of a stiffening stylet to assist in implantation.

These small diameter endocardial pacing and cardioversion/defibrillationleads are advantageously sized to be advanced into the coronary sinus tolocate the distal electrode(s) adjacent to the left atrium or intocoronary veins branching from the coronary sinus to locate the distalelectrode(s) adjacent to the left ventricle. The distal end of such acoronary sinus lead is advanced through the superior vena cava, theright atrium, the valve of the coronary sinus, the coronary sinus, and,if employed to pace or sense the left ventricle, into a cardiac veinbranching from the coronary sinus.

Typically, such small diameter endocardial leads are formed with anactive fixation helix that extends distally and axially in alignmentwith the lead body to a sharpened distal tip and that has a helixdiameter substantially equal to the lead body diameter. The fixationhelix does not necessarily increase the overall diameter of theendocardial lead and is relatively robust, once the helix is screwedinto the myocardium. Typically, but not necessarily, the fixation helixis electrically connected to a lead conductor and functions as apace/sense electrode. In some cases, the lead body encloses one or morehelical coiled or stranded wire conductor and lacks a lumen.

The lead bodies of such small diameter endocardial screw-in leads are sosupple and flexible that it is difficult to rotate the lead distal endby application of rotary torque to the lead proximal end unless the leadbody remains relatively straight and not confined by contact with vesselwalls. This diminished “torqueability” prevents the rotation of thefixation helix at the lead distal end or renders the rotation unreliableonce the lead body is advanced through a tortuous pathway and confinedby contact against the vessel walls. To the degree that rotation torquecan be transmitted from the lead proximal end to the lead distal end,the active fixation helix at the lead distal end can be over-rotated andscrewed through the myocardium or under-rotated and not screwed into themyocardium sufficiently. In addition, such lead bodies also possesslittle if any column strength and lack “pushability”, that is theability to advance the lead distal end axially when the lead proximalend is pushed axially, particularly when the lead body extends throughthe tortuous transvenous pathway. Thus, it has been found necessary touse implantation instruments or tools that compensate for the lack ofpushability and torqueability of the lead body.

Once the implantation site is reached in coronary vasculature, it isdifficult to aim the distal fixation mechanism toward myocardial tissue,and the fixation mechanism may inadvertently be aimed at and deployedoutside the myocardium. The pace/sense electrodes may not be in intimatecontact with excitable cardiac tissue, resulting in unduly highstimulation thresholds and diminished sensing. Fixation may be achievedtemporarily, but fixation may be lost over time resulting indislodgement of the pace/sense electrode(s). The fixation mechanism mayperforate through a coronary vessel wall into the pericardial spaceresulting in perforation of the vessel.

SUMMARY

The present invention provides a multi-lumen guide catheter that can beemployed to introduce and locate an electrode of a cardiac lead at adesired implantation site in a coronary blood vessel that satisfiesthese needs. The multi-lumen guide catheter includes an elongated,multi-lumen catheter body having a catheter body proximal end coupled toa handle or hub and extending to the catheter body distal end. Themulti-lumen guide catheter body includes at least one relatively largediameter delivery lumen and a relatively small diameter guide lumen thatextend side-by-side through a proximal portion of the guide catheterbody. A distal portion of the guide catheter body encloses and extendsthe guide lumen to a guide lumen exit port distal to a delivery lumenexit port at the junction of the proximal and distal portions of theguide catheter body. A guide tool is inserted into or received withinthe guide lumen.

At least a portion of the guide catheter is shaped to preferentiallyurge the delivery catheter lumen exit port toward the vessel wall andthe underlying heart and away from the pericardium and pericardial spaceduring advancement of the guide catheter body through coronary vessels.For example, the guide catheter body is shaped in one or more segmentthereof such that the delivery lumen exit port is oriented or biasedinward toward the myocardium and not outward toward the pericardial sacor pericardium as the guide catheter is advanced through a coronaryblood vessel that extends over the epicardium of the heart. Thisorientation of the delivery lumen exit port enables advancement of anactive fixation mechanism of a cardiac lead out of the delivery lumenexit port and through the vessel wall and epicardium into themyocardium. The guide tool can be retracted through the guide lumenbefore or after advancement and fixation of the active fixationmechanism, and the guide catheter can then be withdrawn over the leadbody without disturbing the fixation.

In use, the cardiac lead is fitted into the delivery lumen, and theguide catheter body is advanced through the tortuous pathway to disposethe delivery lumen exit port facing toward the vessel wall overlying theselected fixation site. The cardiac lead is advanced distally to extendthe distal fixation mechanism through the delivery lumen exit port. Thefixation mechanism is actuated to affix the fixation mechanism throughthe vessel wall into myocardial tissue, and the guide catheter body andguide tool within the guide lumen are retracted from the coronaryvasculature and from the body.

In one embodiment, the delivery lumen exit port is formed through acatheter body sidewall. At least a segment of the guide catheter body isshaped to preferentially urge the delivery catheter lumen exit porttoward the vessel wall and the underlying heart and away from thepericardium during advancement of the guide catheter body throughcoronary vessels. The distal fixation mechanism of the cardiac lead isadvanced out of the delivery lumen exit port toward the heart andadvantageously fixed into the myocardium.

In a variation of this embodiment, the multi-lumen guide catheter bodyincludes two delivery lumens extending through the proximal portion ofthe catheter body to two delivery lumen exit ports formed through thecatheter body sidewall spaced apart longitudinally from one another. Theshaped guide catheter body urges the delivery lumen exit ports towardthe heart. Advantageously, two cardiac leads can be advanced to twospaced apart sites within the coronary vasculature, and the distalfixation mechanisms can be independently advanced out of each deliverylumen exit port toward the heart and fixed into the myocardium.

In certain embodiments, the guide catheter body is reduced in diameterin the distal portion extending between the delivery lumen exit port andthe guide lumen exit port and at the catheter body distal end, alsoreferred to herein as a “distal leader”. Consequently, the smalldiameter distal leader can be advanced readily over a guide wireinserted into the guide lumen through twists and turns of the tortuouspathway and thereby guides the advancement of the larger diameterproximal segment of the catheter body. The small diameter distal leadercan also be advanced deeply into narrow pathways or passages to disposethe more proximal delivery lumen exit port at a desired implantationsite.

The guide tool includes a guide wire that has already been advancedthrough the tortuous pathway. However, the guide tool can be a removablestiffening stylet that can be manually shaped to impart a bend in thedistal segment of the guide catheter and can be inserted or withdrawnfrom the guide lumen, or (in certain embodiments) a pull wire coupled atthe distal end of the guide lumen and extending proximally through theguide lumen. The guide lumen exit port can be left open to provide foruse either with a guide wire in an over-the-wire introduction or with aremovable stiffening stylet. Alternatively, the guide lumen exit portcan be closed for use with a removable stiffening stylet or a fixed pullwire. The stiffening stylet can be provided with a selectable shape toenable advancement through the tortuous pathway or disposition of thedelivery lumen exit port and at a selected implantation site. Or, asteerable stylet having a distal segment in which a bend can beselectively imparted or removed by manipulation of a proximal handle canadvantageously be employed to impart a bend in the distal leader of thecatheter body to steer it through bends and turns of a tortuous pathway.

The guide catheters and methods of the present invention advantageouslysimplify introduction of cardiac leads that lack a lumen for receiving astiffening stylet and lack sufficient column strength to be pushed to adesired implantation site. The implantation sites include any selectedimplantation sites of the coronary sinus and the cardiac veinsdescending from the coronary sinus accessed through a transvenouspathway.

This summary of the invention and the advantages and features thereofhave been presented here simply to point out some of the ways that theinvention overcomes difficulties presented in the prior art and todistinguish the invention from the prior art and is not intended tooperate in any manner as a limitation on the interpretation of claimsthat are presented initially in the patent application and that areultimately granted.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects and features of the present invention will be readilyappreciated as the present invention becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawings, in which like referencenumerals designate like parts throughout the figures thereof andwherein:

FIG. 1 is a schematic diagram of a heart from an anterior perspectiveillustrating the coronary venous system about an epicardial surface ofthe heart, including dashed lines depicting a portion of coronary venoussystem on an opposite, posterior epicardial surface of the heart;

FIG. 2 is a plan view, in partial exposed section, of a typical pacinglead that can be introduced and affixed in the coronary venous systememploying a bitumen guide catheter and method of the present invention;

FIG. 3 is a plan view of a guide wire and an over-the-wire bilumen guidecatheter in accordance with a first embodiment of the invention adaptedto be advanced through the tortuous pathway from outside the patient'sbody to the implantation sites illustrated in FIG. 1, for example, overthe guide wire;

FIG. 4 is a partial view of a distal segment of the catheter body ofFIG. 3 depicting the leader, the delivery lumen exit port, and the guidewire extending from the guide lumen exit port;

FIG. 5 is a cross-section view taken along lines 5-5 in FIG. 4 depictingthe shape of at least a portion of the catheter body to preferentiallyurge the delivery catheter lumen exit port toward the vessel wall andthe underlying heart and away from the pericardium and pericardial spaceduring advancement of the guide catheter body through coronary vesselsdepicted in FIG. 1;

FIG. 6 is a cross-section view taken along lines 6-6 in FIG. 4 depictingthe shape of the delivery catheter lumen exit port to urge the distalfixation helix of the cardiac lead of FIG. 2 toward the vessel wall andthe underlying heart and away from the pericardium and pericardial spaceduring advancement of the guide catheter body through coronary vesselsdepicted in FIG. 1;

FIG. 7 is a partial perspective view of a further embodiment of abi-lumen catheter body adapted to be combined with a hub of the typedepicted in FIG. 3, the catheter body shaped to optimally dispose thedelivery lumen exit port toward the heart;

FIG. 8 is a partial schematic illustration of the disposition of thedelivery lumen exit port of the catheter body of FIG. 7 toward the heartto affix the fixation helix of the cardiac lead of FIG. 2 when the guidecatheter body is advanced through the tortuous pathway from outside thepatient's body to the implantation sites illustrated in FIG. 1;

FIG. 9 is a partial plan view of a multi-lumen catheter body having atleast two delivery lumens that is adapted to be substituted for thecatheter body of the guide catheter of FIG. 3, with suitablemodification of the hub;

FIG. 10 is a partial schematic illustration of the disposition of thedelivery lumen exit ports of the catheter body of FIG. 9 toward theheart to affix the fixation helices of two cardiac leads of FIG. 2 whenthe guide catheter body is advanced through the tortuous pathway fromoutside the patient's body to the implantation sites illustrated in FIG.1;

FIG. 11 is a partial perspective view of a further embodiment of abi-lumen catheter body adapted to be combined with a hub of the typedepicted in FIG. 3, the catheter body shaped to optimally dispose thedelivery lumen exit port toward the heart;

FIG. 12 is a cross-section view taken along lines 12-12 of FIG. 11depicting one form of internal shaping of the catheter body proximalportion;

FIG. 13 is a partial schematic illustration of the disposition of thedelivery lumen exit port of the catheter body of FIG. 11 toward theheart to affix the fixation helix of the cardiac lead of FIG. 2 when theguide catheter body is advanced through the tortuous pathway fromoutside the patient's body to the implantation sites illustrated in FIG.1; and

FIG. 14 is a cross-section view taken along lines 12-12 of FIG. 11depicting a further form of internal shaping of the catheter bodyproximal portion.

The drawing figures are not necessarily to scale.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the following detailed description, references are made toillustrative embodiments for carrying out the invention. It isunderstood that other embodiments may be utilized without departing fromthe scope of the invention. The invention and its preferred embodimentsmay be employed in implantation of unipolar, bipolar or multi-polar,endocardial, cardiac pacing leads, cardioversion/defibrillation leads ormonitoring leads having one or more pace/sense electrode(s) or senseelectrode(s), respectively, at or adjacent the distal lead end and anactive fixation mechanism that is to be affixed into the myocardium.Moreover, other sensors for sensing a physiologic parameter may beincorporated into the lead body. An insulated electrical conductorextending proximally through the lead body to connector element of alead proximal end connector assembly is coupled to each such pace/senseelectrode, sense electrode, cardioversion/defibrillation electrode andsensor. The proximal connector assembly is adapted to be coupled to theconnector assembly of an external medical device, including an externalpacemaker or monitor, or an implantable medical device, including an IPGfor pacing, cardioversion/defibrillation (or both) or an implantablemonitor. Therefore, it will be understood that the arrangement forintroduction of a cardiac lead of the present invention can be employedto introduce permanently implantable and temporary cardiac leads of anyof these types, particularly within the coronary vasculature.

The multi-lumen guide catheters and methods of the present invention areparticularly useful in introducing such small diameter cardiac leadsthat are devoid of a stylet lumen and are so flexible and possess suchlow column strength, rigidity, pushability and torqueability that thelead distal end cannot be advanced transvenously and positioned at thedesired implantation site without assistance. Moreover, one particularuse of the arrangement of the present invention is to introduce suchcardiac leads that are formed using stranded wire conductor(s) within alead body diameter of about 0.010-0.026 inches of the type described inthe commonly assigned U.S. Pat. No. 5,246,014, herein incorporated byreference in its entirety. The lead body outer diameter is minimized byuse of such conductors and by eliminating the lumen for receiving astiffening stylet. However, the arrangement of the present invention canalso be employed to introduce cardiac leads that employ coiled wireconductors with or without a lumen for receiving a stiffening stylet. Inthe latter case, the stiffening stylet need not be used to achieve theintroduction.

FIG. 1 is a schematic diagram of a heart 6 from an anterior perspectiveillustrating a coronary venous system about an epicardial surface,including dashed lines depicting a portion of coronary venous system onan opposite, posterior surface of the heart 6. FIG. 1 also illustrates apathway, defined by arrow ‘A’, which may be followed in order to place acardiac lead within CS 4, extending from a venous access site (notshown) through the superior vena cava (SVC) 1 into the right atrium (RA)2 of heart 6 and from the RA 2 into the CS 4 through a coronary sinusostium (CS Os) 3.

As illustrated in FIG. 1, the coronary venous system of a heart 6includes the CS 4 and vessels branching therefrom including the middlecardiac vein (MCV) 13, the posterior cardiac vein (PCV) 12, theposterior-lateral cardiac vein (PLV) 11, the great cardiac vein (GCV) 9,and the lateral cardiac vein (LCV) 10 all branching away from the CS 4.Generally speaking, the distal portion of the CS 4 and the branchingvessels including at least portions of the MCV 13, PCV 12, the PLV 11,the GCV 9, and the LCV 10 overlie the or are embedded within theepicardium that defines outer surface of the heart 6 and encases heartmuscle or myocardium. Portions of the epicardium are spaced from asurrounding pericardial sac or pericardium (not shown), whereby apericardial space surrounds the spaced epicardium of heart 6. Thus, thevessel walls of the distal portion of the CS 4 and the branching vesselsincluding at least portions of the MCV 13, PCV 12, the PLV 11, the GCV9, and the LCV 10 are partially exposed to the pericardial space oradhered to the pericardium and are partially embedded against theunderlying myocardium. For convenience of terminology, the vessel wallsthat are disposed toward the pericardium are referred to as disposed“away from the heart”, whereas the vessel walls that are disposed towardthe myocardium are referred to as disposed “toward the heart”.

In patients suffering from heart failure, a CS lead of the typesdescribed above is advanced through the pathway “A” extending throughthe SVC 1 and RA 2 into the CS 4 to dispose one or a pair of distalpace/sense electrodes at an LV site(s) within one of the vesselsbranching from the CS 4. An RV lead is advanced through the SVC 1, theRA 2, the tricuspid valve, and the distal pace/sense electrode(s) isaffixed at an RV pace/sense site(s) of the RV 8, e.g., in the RV apex oralong the septum separating the RV and LV chambers. The RV lead can takeany of the functions known in the art preferably having an active orpassive fixation mechanism.

The proximal connectors of the CS lead and the RV lead are coupled to aconnector header of a pacing IPG or an ICD IPG (not shown) implantedsubcutaneously. The IPG is capable of sensing and processing cardiacsignals detected at the pace/sense site(s) to provide synchronized RVand LV pacing at the pace/sense sites as needed. The pacing and sensingfunctions of such an IPG that provides synchronous activation of the RV8 and LV 7 in order to improve the hemodynamic output of the heart 6 aredisclosed in commonly assigned U.S. Pat. No. 5,902,324, for example, andare embodied in the MEDTRONIC® InSync Marquis™ ICD IPG, for example.

Hemodynamic output is enhanced when the CS pace/sense electrode(s) siteis selected within a late activated region of LV 7. Late activatedregions of the LV 7 are found within the myocardium underlying the PLV11, the LCV 10, the GCV 9, or the CS 4 near a junction with the GCV 9.Moreover, pacing and sensing functions are optimized when the pace/senseelectrode(s) are disposed in intimate contact with excitable myocardialtissue.

The lead body of a permanent or temporary cardiac lead typicallyincludes one or more insulated conductive wire surrounded by aninsulating outer sheath. Each conductive wire couples a proximal leadconnector element with a distal stimulation and/or sensing electrode.Temporary and permanent cardiac leads having a single stimulation and/orsensing electrode at the lead distal end, a single conductor, and asingle connector element are referred to as unipolar cardiac leads.Temporary and permanent cardiac leads having two or more stimulationand/or sensing electrodes at the lead distal end, two or more respectiveconductors, and two or more respective connector elements are referredto as bipolar lead or multi-polar leads, respectively.

A typical example of an active fixation cardiac lead 20 that can beintroduced through a bilumen guide catheter of the present inventionadvanced through pathway “A” and employed as a CS lead is schematicallyillustrated in FIG. 2. The cardiac lead 20 can also be introduced asdescribed above into the RV to function as an RV lead. The cardiac lead20 has an elongated lead body 21 that extends between a proximalconnector 22 and a distal end 24. A helical fixation element or helix 25having a sharpened piercing tip 251 extends distally from lead bodydistal end 24. Pacing lead 20 is essentially iso-diametric along itslength, with an outer diameter of lead body 21 and fixation helix 25between approximately 1 French (0.33 mm) to 3 French (1.00 mm). Sincelead body 21 does not include an inner lumen, the outer diameter of leadbody 21 is reduced.

Lead body 21 is constructed of a stranded conductive or non-conductivefilament cable 28 disposed within an inner sheath lumen of an innersheath 29, which in turn extends through the coil lumen of a coil 27.The assembly of the coil 27, inner sheath 29, and cable 28 is fittedthrough an outer sheath lumen of an outer sheath 26.

Coil 27 is formed of any bio-stable and biocompatible material that issufficiently stiff to provide adequate torque transfer from proximalconnector assembly 22 to fixation element 25 at distal end 24 of cardiaclead 20. When coil 27 functions as a lead conductor, coil 27 ispreferably formed of single or multiple wire filars made of MP35-Nalloy, well known in the art, or any other bio-stable and biocompatiblematerial that is capable of reliably conducting electrical current afterhaving been subjected to numerous, repeated bending and torsionalstresses.

Inner cable 28 is formed from synthetic filaments or conductive metallicwires, when inner cable functions as a lead conductor. The proximal anddistal ends of inner cable 28 are coupled to connector pin 23 or withinconnector assembly 22 and fixation helix 25, respectively, to providetensile strength to lead body 21.

Outer sheath 26 is formed of either a silicone rubber or polyurethane,well known in the art, or any other flexible, bio-stable andbiocompatible, electrically insulating, polymer material. Inner sheath29 is similarly formed of a bio-stable and biocompatible flexiblepolymer coating or tube that protects inner cable 28 from mechanicalstresses or degradation and electrically insulates inner cable 28 fromcontact with wire coil 27. Inner sheath 29 can be formed of flexible,bio-stable and biocompatible electrically insulating materials known inthe art, including silicone rubber compounds, polyurethanes, andfluoropolymers.

In both unipolar and bipolar cardiac lead embodiments, the proximalconnector assembly 22 includes a connector pin 23 that is typicallyelectrically connected with the distal fixation helix 25 when the distalfixation helix 25 functions as a pace/sense electrode. In a bipolarcardiac lead embodiment, the proximal connector assembly 22 includes aconnector ring 32 (shown with dashed lines) that is electrically coupledto a ring-shaped pace/sense electrode 30 (shown with dashed lines)supported by outer sheath 26 proximal to fixation helix 25. Theconnector assembly 22 is shaped to be inserted into a bore of aconnector block of the connector header of an IPG as described above tomake an electrical connection between the distal pace/sense electrode(s)and IPG sensing and/or pacing pulse generating circuitry. Ring-shapedpace/sense electrode 30 is preferably formed of a platinum alloy butother materials may also be used, including but not limited to suchmaterials as palladium, titanium, tantalum, rhodium, iridium, carbon,vitreous carbon and alloys, oxides and nitrides of such metals or otherconductive or even semi-conductive materials. Of course, some materialsare incompatible with others and may not be effectively used together.The limitations of specific materials for use with others are well knownin the art.

The fixation helix 25 is adapted to be screwed into the myocardium, asdescribed below, by rotation of lead body 21 from the proximal connectorassembly 22 when piercing tip 251 is advanced to and oriented toward afixation site. When fixation helix 25 functions as a pace/senseelectrode, as in alternate embodiments described above, fixation helix25 is preferably formed of a platinum iridium alloy, although it isunderstood that other biocompatible and bio-stable materials may also beused, including but not limited to such materials as palladium,titanium, tantalum, rhodium, carbon, vitreous carbon and alloys, oxidesand nitrides of such metals or other conductive or even semi-conductivematerials well known in the art.

In a unipolar embodiment of cardiac lead 20, the inner cable 28 isnonconductive, a proximal end of coil 27 is coupled to connector pin 23,and a distal end of coil 27 is coupled to the proximal end of fixationhelix 25. The proximal and distal ends of coil 27 are welded or crimpedto the connector pin 23 and fixation helix 25, respectively, usingcommon welding or crimping techniques known in the art. The proximal anddistal ends of inner cable 28 are crimped to the connector pin 23 orconnector assembly 22 and fixation helix 25, respectively, using commonwelding or crimping techniques known in the art.

In an alternate unipolar embodiment wherein the inner cable isnonconductive, helix fixation element 25 simply provides fixation anddoes not function as a pace/sense electrode. The proximal end of coil 27is coupled to connector pin 23, and the distal end of coil 27 is coupledto the ring-shaped pace/sense electrode 30 incorporated coaxially abouta distal portion of lead body 21. The spacing 31 between ring-shapedpace/sense electrode 30 and fixation helix 25 is less than approximately0.02 inches, in order to locate ring-shaped pace/sense electrode 30close enough to a fixation site for tissue contact when fixation helix25 is fixed into the myocardium.

In a further alternate unipolar embodiment of cardiac lead 20, innercable 28 is electrically conductive, and the proximal and distal cableends are electrically coupled by crimping or welding or other knowntechniques to connector pin 23 and helix fixation element 25,respectively. Inner sheath 29 electrically insulates inner cable 28 fromcoil 27, which acts only as a structural element to provide torsionalstiffness to lead body 21. Alternatively, the proximal and distal endsof the conductive inner cable 28 and the wire coil 27 can beelectrically connected together to provide a redundant unipolar leadconductors. Conductive inner cable 28 is preferably formed from wirestrands or filaments made of MP35-N alloy, well known in the art, or anyother bio-stable and biocompatible material that is capable of reliablyconducting electrical current after having been subjected to numerous,repeated bending and torsional stresses.

In a bipolar embodiment of cardiac lead 20, both coil 27 and inner cable28 are lead conductors as described above, that are electricallyinsulated from one another by inner sheath 29. In this embodiment, theproximal and distal ends of coil 27 are electrically and mechanicallycoupled by crimping or welding to the connector ring 32 and thering-shaped pace/sense electrode 30, respectively. The proximal anddistal ends of the inner cable 28 are electrically and mechanicallycoupled by crimping or welding to connector pin 23 and distal fixationhelix 25, respectively. The spacing 31 between ring-shaped pace/senseelectrode 30 and fixation helix 25 is between approximately 0.2 inchesand 0.4 inches, a range well known in the pacing art for inter-electrodebipolar pace/sense electrode spacing.

The exemplary active fixation cardiac lead 20 can also be formed havingan elongated cardioversion/defibrillation (C/D) electrode extendingproximally a predetermined distance along the outer sheath 21 from a C/Delectrode distal end located proximal to distal lead end 24. Theproximal and distal ends of the wire coil 27 would be electrically andmechanically coupled to the connector ring 32 and the elongated C/Delectrode, respectively. The proximal and distal ends of the inner cable28 would be electrically and mechanically coupled by crimping or weldingto connector pin 23 and distal fixation helix 25, respectively.

A means for steroid elution may be incorporated into any of theaforementioned embodiments of the exemplary active fixation cardiac lead20 near distal end 24. Such steroid elution means may take the form of amonolithic controlled release device (MCRD), constructed, for example,from silicone rubber and loaded with a derivative of dexamethasone, suchas the water-soluble steroid dexamethasone sodium phosphate. MCRDconstruction and methods of fabrication are found in commonly assignedU.S. Pat. Nos. 4,506,680, 4,577,642, 4,606,118, and 4,711,251.Alternatively a steroid coating containing a no more than sparinglywater-soluble steroid such as beclomethasone diproprionate ordexamethasone acetate may be applied to surfaces of ring-shapedpace/sense electrode 30 and/or fixation helix 25. A steroid coatingcomposition and method of application is found in commonly assigned U.S.Pat. No. 5,987,746. The steroid coating may be applied directly tosurfaces or portions of surfaces preserving structural integrity ofring-shaped pace/sense electrode 30 and/or fixation helix 25 and takingup less space than an MCRD.

Such an exemplary active fixation cardiac lead 20 can be employedadvantageously as a CS lead through the use of the bilumen guidecatheters of the present invention advanced through the pathway “A” ofFIG. 1 to locate the fixation helix 25 at a fixation site in thecoronary vasculature and to aim the helix tip 251 toward the heartbefore the connector assembly 22 is rotated to screw the fixation helix25 through the vessel wall and into the myocardium.

The guide catheters of the present invention enable the implantation ofa small diameter lead body 21 in the range of 1 French (0.33 mm) to 3French (1.00 mm), but it will be understood that the over-the-wire guidecatheters can be sized to facilitate implantation of larger diameterlead bodies exceeding 3 French in diameter. It will be understood thatthe guide catheters and methods of use disclosed herein can be employedto introduce and secure any form of distal fixation hooks or fixationhelices either extending distally like distal fixation helix 70 orlaterally from the lead body in the manner of those distal fixationhelices disclosed in U.S. Pat. Nos. 3,835,864 and 4,233,992, forexample. It will be understood that other active fixation cardiac leadshaving differing shaped fixation mechanisms, e.g., barbs or prongs orpins, can also be advantageously employed with the bitumen guidecatheters of the present invention. For example, the guide catheters ofthe present invention can be employed to locate the fixation mechanismat a fixation site in the coronary vasculature and to aim a fixationmechanism toward the heart before the proximal connector assembly or afurther device is activated or manipulated to advance and drive thefixation mechanism through the vessel wall and into the myocardium.

Turning to FIGS. 3-6, a first embodiment of an exemplary elongatedbilumen guide catheter 100 adapted to be used with a guide toolincluding a guide wire 80, for example, is illustrated. The guide wire80 extends between a guide wire proximal end 82 and a guide wire distalend 84 and is adapted to be advanced through the tortuous pathway “A”from outside the patient's body to the implantation sites illustrated inFIG. 1, for example. The bilumen guide catheter 100 depicted in FIG. 3includes an elongated catheter body 102 extending from a catheter bodyproximal end 112 joined with proximal handle or hub 110 to a catheterbody distal end 118. The elongated catheter body 102 has a length ofabout 25 cm to 120 cm depending upon the length of the selected pathwayfrom the skin incision through the patient's body to the implantationsite. The catheter body 102 further includes a proximal portion 108 anda distal portion or leader 120 that are joined together at junction 124as shown in FIG. 6. The distal leader 120 may have a length on the orderof about 10 mm to about 25 mm.

The bitumen guide catheter 100 receives a small diameter cardiac lead,e.g., cardiac lead 20, during the advancement of the catheter body 102through the tortuous pathway “A” and facilitates fixation of the distalhelix 25 at the selected implantation site as shown in FIG. 6. Theadvancement is facilitated by advancement of the small diameter distalleader 120 of the guide catheter 100 over the previously placed guidewire 80 past the selected implantation site.

The catheter body 102 therefore encloses a delivery lumen 114 extendingbetween a guide lumen entry port at the catheter body proximal end 112within the hub 110 and the catheter body distal end 118. The deliverylumen diameter is sized to receive the guide wire 80 inserted therein toaid in steering the guide catheter body 102 through the tortuous pathway“A”. The proximal portion of the catheter body 102 encloses deliverylumen 114 extending between a delivery lumen entry port at catheter bodyproximal end 112 within hub 110 and a delivery lumen exit port 134disposed along the catheter body proximal to the catheter body distalend 118.

To some degree, the disposition of the delivery lumen 114 and a guidelumen 116 extending side-by-side through a circular catheter body 108will cause the catheter body 102 to preferentially bend in a directionthat is transverse to a geometric axis plane AP (shown in FIG. 5)defined by the parallel lumen axes, particularly when advanced through atortuous pathway “A”. In one approach, the catheter body 102 is shapedto overcome that preferential bending tendency to cause the catheterbody 102 to preferentially bend in a fashion to bias the delivery lumenexit port 134 toward the vessel wall. Various shaping techniques andshapes are set forth in the preferred embodiments.

The proximal portion 108 is extruded into the shape depicted in FIG. 5,for example, to have a non-circular cross-section and to incorporateguide lumen 116 and delivery lumen 114. The non-circular cross sectioncan be achieved by a flange 104 presenting a flattened surface extendingalong at least a segment of the proximal portion 108 in a planeorthogonal or transverse to the axis plane AP defined by the axes of thedelivery and guide lumens 114 and 116. The flattened surface of flange104 has an extended width, for example, that encourages bending of theproximal portion 108 in one direction in the fashion of a belt. Theflattened surface of flange 104 can be formed alongside the guide lumen116 as shown in FIG. 5 or can be formed alongside the delivery lumen114. Or the catheter body can be shaped to have two generally parallelflat surfaces that are generally orthogonal to the plane defined by theaxes of the delivery and guide lumens 114 and 116. The flange 104 neednot extend the full length of the proximal portion 108 of the catheterbody 102 but may be present in a segment thereof that would be expectedto be advanced, in use, into a coronary blood vessel.

The catheter body 102 is reduced in cross-section area diameter in thedistal leader 120 extending between the delivery lumen exit port 134 andthe guide lumen exit port 136. The distal leader 120 can be tubular incross-section and tapered distally to facilitate advancement over theguide wire 80 extending through the guide lumen 116. Consequently, thesmall diameter leader 120 can be advanced readily over guide wire 80through twists and turns of the tortuous pathway and thereby guides theadvance of the larger cross-section proximal segment 108 of the catheterbody 102. The small diameter leader 120 can also be advanced deeply intonarrow pathways or passages to dispose the more proximal delivery lumenexit port 134 at a desired implantation site. The flattened surface 104encourages bending of the proximal portion 108 to track the contours ofthe heart and dispose the delivery lumen exit port 134 aimed toward theheart. The leader 120 can be straight or have one or more preformed bendalong the length thereof.

Then, as shown in FIG. 6, the fixation helix 25 can be advanced out ofthe delivery lumen exit port 134 extending away from the axis of thedelivery lumen 114 and toward the heart. The sharpened tip 251 of thefixation helix 25 can then be advanced, as the lead connector assemblyis rotated, through the vessel wall and into the underlying myocardium.Fixation is achieved as the fixation helix 25 is screwed into themyocardium.

FIG. 6 also illustrates a further form of shaping of a segment of thecatheter body 102 to bias the delivery lumen exit port 134 toward thevessel wall as the fixation helix 25 is advanced out of the deliverylumen exit port 134. The distal end of the delivery lumen is curved intoa guide bend 135 just proximal to the delivery lumen exit port 134 sothat the sharpened tip 251 extends toward the vessel wall as thefixation helix 25 is advanced out of the delivery lumen exit port 134.

The hub 110 (FIG. 3) coupled to the guide catheter proximal end 112 cantake the form of the hub disclosed in co-pending U.S. application Ser.No. 10/319,245. The hub 110 is advantageously formed with a hub deliverylumen mating to the delivery lumen proximal end opening and axiallyaligned with the catheter body delivery lumen 114. The hub deliverylumen extends through the hemostasis valve 140 and a hub guide lumendefined by a hub guide tube 122 extending through a side extension 132of the hub 110.

The hemostasis valve 140 includes a proximal rotating closure knob 142,an intermediate side port (extension hose and stopcock not shown) 144and a distal rotating locking collar (for securing valve to luer hubfitting) 146 that is press fit onto the hub 110. The knob 142 and sideport 144 and collar 146 are used in the fashion of a standard hemostasisvalve manufactured by numerous suppliers to shut off the flow and tolock the lead or other catheter in relation to the catheter body. Thevalve 140 provides a lead insertion lumen axially aligned with the hubdelivery lumen 148 so that a cardiac lead 20 of the types describedabove can be inserted therethrough and into the catheter body deliverylumen 114.

The hub guide tube 122 extends in an arcuate path through window 150 andthe side extension 132 that can also be coupled with a Luer typehemostasis valve to seal around the guide wire 80 in a manner well knownin the art. The hub 110 and the catheter body 102, particularly theproximal portion 108, are formed to be slittable along the lengthsthereof to exposed the aligned hub and catheter body delivery lumens andrelease the lead body of the cardiac lead 20 in a manner described inthe above-referenced '346 and '433 patents. An enlarged, relatively flatpad or paddle 130 is formed extending away from the hemostasis valve 140and the hub guide tube 122 that can be gripped on either side by thefingers to assist in holding and manipulating the hub 110 duringadjustment of the hemostasis valve 140 and advancement of the catheterbody assembly of the cardiac lead 20 and catheter body 102 through thetortuous pathway over the guide wire 80.

The guide wire 80 may have an outer diameter in the range of 0.014 to0.016 inches. The guide wire 80 can be a guide wire that is eitherintroduced by itself or is introduced through a separate, small diameterintroducer, e.g., a COOK® RoadRunner® Extra Support guide wire having anouter diameter of 0.018 inches (0.49 mm). The guide wire 80 can also bea deflectable or steerable guide wire of the type disclosed in commonlyassigned U.S. Pat. No. 4,815,478, for example.

The bilumen guide catheter 100 depicted in FIGS. 3-6 can also beadvanced through the tortuous pathway “A” of FIG. 1 employing astiffening stylet or steerable stylet substituted for guide wire 80inserted into guide lumen 116 to stiffen and selectively bend the distalleader 120 to during such advancement. In this variation, the guidelumen exit port is preferably closed or blocked by a block 138 toinhibit the ingress of blood and fluids.

A typical stylet includes a stainless steel wire extending between aproximal stylet wire handle and stylet wire distal end. The stylet wireis adapted to be advanced through the hub guide lumen 125 and thecatheter guide lumen 116 from outside the patient's body to abut thestylet distal end against the blockage 138 at the catheter body distalend 118. The stylet wire may have a stylet diameter of about 0.012 to0.016 inches. The stylet may be a steerable stylet, e.g., the MEDTRONIC®Model 9210 steerable stylet or a steerable stylet of the types disclosedin commonly assigned U.S. Pat. Nos. 5,873,842 and 6,146,338.

Certain embodiments of the bilumen catheter body 102 can advantageouslybe formed by extrusion of a single polymeric material without thenecessity of reinforcement or changing material characteristics alongits length. The bilumen catheter body 102 can be extruded from medicalgrade thermoplastic resins of 35D Shore durometer, for example, to formthe delivery tube 104 joined to a guide tube 106 at the elongatedjunction 108. A radiopaque marker band can be incorporated at thecatheter body distal end 118 at the distal tip of the distal leader 120.

The proximal portion 108 can be extruded from medical gradethermoplastic resins of 70D-75D Shore durometer, for example, and thedistal leader 120 can be extruded from medical grade thermoplasticresins of 75A-35D Shore durometer, for example. The durometer of theproximal portion 108 is therefore lower than the durometer of the distalleader 120. The higher durometer of the distal leader 120 enables it tobe formed having a thin sidewall so that the distal leader 120 can bemade smaller in diameter while providing a suitable guide lumen diameterto track a guide wire or receive a stylet or to be directed into smallerdiameter blood vessels or other body tracts. The harder surface of thehigher durometer material tends to have lower contact stress and, thus,presents lower friction to the guide wire. Moreover, the higherdurometer distal leader 120 can be shaped to have a pre-formed bend orcurvature that is assumed upon retraction of the guide wire and assistsin urging the delivery lumen exit port 134 toward the heart. The medicalgrade thermoplastics can be selected from polyether block amide (PEBA),polyamide (PA), polyurethane (PU), polyester (PET), polybutyleneterephthalate (PBT), or polyvinyl chloride (PVC). Optimally, theproximal portion 120 can be extruded from one of the group consisting ofPEBA, PU, PET or PVC having a relatively low durometer, whereas thesmaller diameter distal leader 120 can be extruded from the groupconsisting of PEBA, PU, PA, PET, PBT or PVC having a relatively higherdurometer.

In addition to the radiopaque marker band, an atraumatic soft tip can beapplied at the catheter body distal end 118. The soft tip can be formedof a polyurethane, e.g., TECOFLEX® TT-1074A polyurethane sold byThermedics Polymer Products, Inc., Woburn, Mass. The polyurethanematerial can be loaded with a radiopaque material, e.g. Barium sulfateor tungsten powder, to make the resulting molded soft tip radiopaque.

The surfaces of delivery lumen 114 and guide lumen 116 may be coatedwith a lubricant to facilitate advancement of a cardiac lead 20 or otherinstrument through the delivery lumen 114 and the guide wire 80 orstylet wire or other instrument through the guide lumen 116. Theexterior surface of a distal portion of the catheter body 102 includingthe distal leader 120 can also be coated with the lubricant tofacilitate advancement of the distal leader 120 through the tortuouspathway. Suitable biocompatible lubricating coatings include asilicone-based lubricant, e.g., a silicone oil, or a reactive siliconelubricant, e.g., MDX4-4159 silicone lubricant available from DowChemical Co., Midland, Mich. Other suitable biocompatible lubricatingcoatings include hydrophilic slip coating materials, e.g.,polyacrylamide, polyvinylpyrrolidone, hyaluronic acid, or polyethyleneoxide.

Referring to FIGS. 7 and 8, a further embodiment of the guide catheter100, particularly having a further catheter body 202 including aproximal portion 208 and a distal leader 220, is shown. In thisembodiment, the proximal portion 208 of catheter body 202 is extrudedinto a substantially oval or rectangular cross-section shape havingopposed major, substantially flat, sides 204 and 205. The delivery lumen214 and guide lumen 216 extend side-by-side through the proximal portion208 between the major sides 204 and 205. The parallel axes of thedelivery lumen 214 and guide lumen 216 define a geometric axis plane AP,and the major sides 204 and 205 extend substantially in parallel withthe axis plane AP. A short distal segment of the delivery lumen 214 isshifted out of side-by-side alignment with a corresponding segment ofthe guide lumen 216 to dispose the delivery lumen exit port 234 above oralongside the major side 204. The axis plane AP is in effect twistedfrom a first orientation prevailing in the proximal segment of theproximal portion 208 into a second orientation near the delivery lumenexit port 234 (as shown in FIGS. 7 and 8) that is substantiallytransverse to the first orientation. The distal end of the deliverylumen 214 can be shaped with a curved guide bend 135 of the typedepicted in FIG. 6.

As shown in FIG. 8, the opposed major sides 204 and 205 tend to causethe catheter body 202 to advance through the coronary vasculature overthe guide tool, e.g., the guide wire 80, within the guide lumen 216 withthe delivery lumen exit port 234 disposed toward the heart. A curve 221is preferably pre-formed in the distal leader 220 extending away fromthe major side 205 that tends to offset the shift of the delivery lumenexit port 234 into alignment with the major side 204 and to dispose thedelivery lumen exit port 234 toward the heart, particularly themyocardium of the LV 7 as also shown in FIG. 8.

The delivery lumen 214 and the guide lumen 216 can constituteco-extruded tubes of the materials described above. The connectionbetween the co-extruded tubes can be severed along the length of thedistal segment of the delivery lumen 214. The distal ends of theco-extruded tubes can be cut to length to form the distal leader 220 andto dispose a short segment of the tube surrounding the delivery lumen214 over a proximal segment of the tube surrounding the guide lumen 216.Or, a distal segment of the proximal portion 208 and the distal leader220 can be molded as a separate assembly that is adhered to a distal endof the substantially rectangular cross-section extrusion to form thecatheter body 202.

A jacket 240 of flat metal or plastic filaments may be braided over theouter surface of the proximal portion 208 of the catheter body 202 thatfurther assists in causing the catheter body to preferentially bend tobias the delivery lumen exit port 234 toward the heart. A thin coatingof elastomeric material can be fitted over the jacket 240 to make itsexterior surface smooth.

Referring to FIGS. 9 and 10, a still further embodiment of the guidecatheter 100, particularly a further catheter body 302 having at leastone further lumen, is shown. In particular, an additional delivery lumen317 is provided in the catheter body proximal portion 308 thatterminates in a further delivery lumen exit port 335. The proximalportion 308 of catheter body 302 is relatively cylindrical toaccommodate three lumens 314, 316 and 317. However, shaping of thecatheter body 302 to urge the delivery lumen exit ports 334 and 335toward the heart is accomplished by shapes formed in segments of theproximal and distal portions 308 and 320 that collectively have ashallow “S” shape including pre-formed bends 319, 321 and 323 as shownin FIG. 10.

Referring to FIGS. 11-14, a still further embodiment of the guidecatheter 100, particularly a further catheter body 402 having aninternal shaping structure, is depicted. In this embodiment, theproximal portion 408 of catheter body 402 is formed of a generallycylindrical outer sheath 442 that encloses a generally oval orrectangular or triangular cross-section, bitumen tube 438 having opposedmajor sides 404 and 405. A delivery lumen 414 and guide lumen 416 extendside-by-side through the tube 438 in proximal portion 408 between themajor sides 404 and 405. Two examples of the cross section of bitumentube 438 are shown in FIGS. 12 and 14 where the major sides 404 and 405are spaced from and extend substantially parallel to the axis plane AP.

A jacket 440 of flat metal or plastic filaments may be braided over theouter surface of the tube 438 in proximal portion 208 of the catheterbody 202 that further assists in causing the catheter body 202 topreferentially bend to bias the delivery lumen exit port 234 toward theheart. In this embodiment, the generally cylindrical outer sheath 442 isformed over the jacket 440 to make the proximal portion 408 of catheterbody 402 generally cylindrical.

A short distal segment of the delivery lumen 414 is shifted out ofside-by-side alignment with a corresponding segment of the guide lumen416 to dispose the delivery lumen exit port 434 above or alongside theflat side 404 in the manner described above with respect to theembodiment of FIGS. 7 and 8. The distal end of the delivery lumen 414can be shaped with a curve like guide bend 135 depicted in FIG. 6.

In this way, the shape of the jacket 440 tends to cause the catheterbody 402 to advance through the coronary vasculature over the guidetool, e.g., the guide wire 80, within the guide lumen 416 with thedelivery lumen exit port 434 disposed or biased toward the heart. Acurve 421 is preferably pre-formed in the distal segment 420 extendingaway from the flat side 405 that tends to offset the shift of thedelivery lumen exit port 434 into alignment with the flat side 404 andto dispose the delivery lumen exit port 434 toward the heart,particularly the myocardium of the LV 7 as also shown in FIG. 12.

These embodiments of bitumen and multi-lumen guide catheters 100 can beemployed in a variety of procedures for introducing cardiac leads intocoronary veins of the heart, e.g., deep in the cardiac veins descendingfrom the coronary sinus accessed transvenously and through the coronarysinus as illustrated in FIG. 2, to lodge the distal pace/sense electrodein relation to the left ventricle. The guide catheters 100 can also beemployed to fix a pace/sense electrode at certain particular sites in aheart chamber, e.g., the right ventricular outflow tract.

Further instruments or diagnostic fluids can be selectively advancedthrough the delivery lumen and/or the guide lumen to facilitateidentification or advancement of the catheter body distal end to theimplantation site preceding the advancement of the cardiac lead throughthe delivery lumen.

The guide catheter having an open guide lumen exit port canadvantageously be used to perform other functions, e.g., to facilitateblocking of a cardiac vessel employing a balloon catheter so thatradiopaque diagnostic fluid can be introduced into the cardiac vessel tovisualize the cardiac vessel in an angiographic procedure in order toidentify a suitable implantation site.

All patents and publications identified herein are incorporated hereinby reference in their entireties.

While particular embodiments of the invention have been disclosed hereinin detail, this has been done for the purposes of illustration only, andis not intended to limit the scope of the invention as defined in theclaims that follow. It is to be understood that various substitutions,alterations, or modifications can be made to the disclosed embodimentswithout departing from the spirit and scope of the claims. The abovedescribed implementations are simply those presently preferred orcontemplated by the inventor, and are not to be taken as limiting thepresent invention to the disclosed embodiments. It is therefore to beunderstood, that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described withoutactually departing from the spirit and scope of the present invention.

1. A guide catheter for introducing a cardiac lead having a distalfixation mechanism through a pathway from an incision to an implantationsite relative to a heart chamber, comprising: an elongated catheter bodyextending between a catheter body proximal end and a catheter bodydistal end, the catheter body having a catheter body sidewall andcomprising a proximal portion and a distal leader extending distallyfrom a distal end of the proximal portion; the catheter body sidewallenclosing a guide lumen having a guide lumen axis and extending betweena guide lumen entry port and the catheter body distal end, the guidelumen diameter sized to receive a guide tool inserted therein to aid insteering the guide catheter body through the pathway; the proximalportion of the catheter body sidewall enclosing a delivery lumen havinga delivery lumen axis and extending between a delivery lumen entry portand a delivery lumen exit port through the catheter body sidewallproximal to the distal leader; the delivery lumen axis and the guidelumen axis extending in a side-by-side manner along a first segment ofthe proximal portion and defining a first geometric axis plane; and theproximal portion of the catheter body sidewall having a cross-sectionalshape comprising a first substantially flat major side extending along asecond segment of the proximal portion of the catheter body in a planethat is transverse to the first geometric axis plane to cause theproximal portion of the catheter body to preferentially bend as thecatheter body tracks a contour of the heart, the catheter bodypreferentially bending in a direction that the delivery lumen exit portis oriented to thereby bias the delivery lumen exit port toward theheart during advancement through the pathway to facilitate passage ofthe fixation mechanism of the cardiac lead through a vessel wall intothe myocardium; wherein the first segment is a distal segment of theproximal portion extending to the delivery lumen exit port; the deliverylumen axis and the guide lumen axis extending in a side-by-side manneralong a third segment of the proximal portion, the third segmentproximal to the first segment; the delivery lumen axis and the guidelumen axis extending along the third segment defining a second geometricaxis plane transverse to the first geometric axis plane.
 2. The guidecatheter of claim 1, wherein the delivery lumen includes a deliverylumen diameter sized to receive the cardiac lead having a lead bodyenclosing a lead conductor and extending between a proximal leadconnector element and a distal electrode to enable introduction of thecardiac lead through the pathway to the implantation site.
 3. The guidecatheter of claim 1, wherein the cardiac lead fixation mechanism is oneof a fixation helix adapted to be screwed through the vessel wall intothe myocardium or a hook or a prong adapted to be extended through thevessel wall into the myocardium.
 4. The guide catheter of claim 1,wherein the guide lumen terminates in a guide lumen exit port in thedistal leader formed to receive a guide tool inserted into the guidelumen as the guide catheter is advanced over the guide tool.
 5. Theguide catheter of claim 1, wherein the first and third segments togetherextend a full length of the proximal portion, wherein the proximalportion of the catheter body preferentially bends in a preferentialbending direction substantially transverse to the first geometric axisplane defined by the delivery lumen axis and the guide lumen axis. 6.The guide catheter of claim 5, wherein the distal end of the deliverylumen is curved into a guide bend proximal to the delivery lumen exitport that deflects the distal fixation mechanism of the cardiac lead outof the first geometric axis plane and toward the preferential bendingdirection.
 7. The guide catheter of claim 1, wherein the distal end ofthe delivery lumen includes a curved portion proximal to the deliverylumen exit port that deflects the distal fixation mechanism of thecardiac lead out of the first geometric axis plane and toward thepreferential bending direction.
 8. The guide catheter of claim 1,wherein the catheter body sidewall includes a flange extendingtransverse to the first geometric axis plane to form the firstsubstantially flat surface that enables the preferential bending of thecatheter body substantially transverse to the first geometric axisplane.
 9. The guide catheter of claim 8, wherein the distal end of thedelivery lumen includes a curved portion proximal to the delivery lumenexit port that deflects the distal fixation mechanism of the cardiaclead out of the first geometric axis plane and toward the preferentialbending direction.
 10. The guide catheter of claim 1 wherein a distalsegment of the delivery lumen is shifted out of the side-by-sidealignment with a corresponding segment of the guide lumen to positionthe delivery lumen exit port along the first substantially flat majorside.
 11. The guide catheter of claim 1 wherein the cross-sectionalshape comprises a second substantially flat major side extendingtransverse to the first geometric axis plane orientation.
 12. The guidecatheter of claim 11 wherein the second substantially flat major sidebeing substantially parallel to the first substantially flat major side.13. The guide catheter of claim 1 further comprising a cylindrical outersheath enclosing the catheter body sidewall.
 14. The guide catheter ofclaim 1 further comprising a jacket of flat filaments braided over anouter surface of the catheter body sidewall.
 15. The guide catheter ofclaim 1 wherein the first segment and the second segment overlap.
 16. Aguide catheter for introducing a cardiac lead having a distal fixationmechanism through a pathway from an incision to an implantation siterelative to a heart chamber, comprising: an elongated catheter bodyextending between a catheter body proximal end and a catheter bodydistal end, the catheter body having a catheter body sidewall andcomprising a proximal portion and a distal leader extending distallyfrom a distal end of the proximal portion; the catheter body sidewallenclosing a guide lumen having a guide lumen axis and extending betweena guide lumen entry port and the catheter body distal end, the guidelumen diameter sized to receive a guide tool inserted therein to aid insteering the guide catheter body through the pathway; the proximalportion of the catheter body sidewall enclosing a delivery lumen havinga delivery lumen axis and extending between a delivery lumen entry portand a delivery lumen exit port through the catheter body sidewallproximal to the catheter body distal end, wherein the delivery lumen andthe guide lumen extend in side-by-side relation through a first segmentof the proximal portion and define a first geometric axis plane, thedelivery lumen shifted out of the side-by-side relation in a distalsegment of the proximal portion to orient the delivery lumen exit portin a direction transverse to the first geometric axis plane, thecatheter body sidewall comprising a cross-sectional shape having atleast one substantially flat major side that extends along at least asegment of the proximal portion of the catheter body in a plane that isparallel to the first geometric axis plane thereby causing the catheterproximal portion to bend in the direction of the delivery lumen exitport as the catheter body tracks a contour of the heart and thereby biasthe delivery lumen exit port toward a blood vessel wall at theimplantation site; wherein the first segment is a distal segment of theproximal portion extending to the delivery lumen exit port; the deliverylumen axis and the guide lumen axis extending in a side-by-side manneralong a second segment of the proximal portion, the second segmentproximal to the first segment; the delivery lumen axis and the guidelumen axis extending along the second segment defining a secondgeometric axis plane transverse to the first geometric axis plane. 17.The guide catheter of claim 16, wherein the distal end of the deliverylumen includes a curved portion forming a guide bend proximal to thedelivery lumen exit port that deflects the distal fixation mechanism ofthe cardiac lead out of the axis plane and toward the preferentialbending direction.
 18. The guide catheter of claim 16, furthercomprising: an inner tube positioned along the first segment of theproximal portion of the guide catheter body enclosing the guide lumenand delivery lumen in side-by-side relation that is shaped to have atleast one major side that extends along at least a segment of theproximal portion of the catheter body substantially parallel with thefirst geometric axis plane, the at least one major side generating thepreferential bending and biasing the delivery lumen exit port toward theheart during advancement of the guide catheter through the pathway tofacilitate passage of the fixation mechanism of the cardiac lead throughthe vessel wall into the myocardium; and an outer sheath formed over theinner tube having a substantially cylindrical sheath outer surface. 19.The guide catheter of claim 18 wherein the inner tube comprisesfilaments braided over an outer surface of the first segment of theproximal portion of the guide catheter body, the braided filamentsformed to assist in causing the catheter body to preferentially bend inthe preferential bending direction.
 20. The guide catheter of claim 16,wherein the delivery lumen has a delivery lumen diameter sized toreceive the cardiac lead to enable introduction of the cardiac leadthrough the pathway to the implantation site.
 21. The guide catheter ofclaim 16, wherein the guide lumen terminates in a guide lumen exit portin the distal leader enabling advancement of the guide catheter over aguide tool inserted into the guide lumen.
 22. The guide catheter ofclaim 16, wherein the guide tool comprises one of a guidewire, astiffening stylet, and a steerable stylet.
 23. A guide catheter forintroducing a cardiac lead having a distal fixation mechanism through apathway from an incision to an implantation site relative to a heartchamber, comprising: an elongated catheter body extending between acatheter body proximal end and a catheter body distal end, the catheterbody having a catheter body sidewall and comprising a proximal portionand a distal leader extending distally from a distal end of the proximalportion; the catheter body sidewall enclosing a guide lumen having aguide lumen axis and extending between a guide lumen entry port and thecatheter body distal end, the guide lumen diameter sized to receive aguide tool inserted therein to aid in steering the guide catheter bodythrough the pathway; and the proximal portion of the catheter bodysidewall enclosing a delivery lumen having a delivery lumen axis andextending between a delivery lumen entry port and a delivery lumen exitport through the catheter body sidewall proximal to the catheter bodydistal end; the guide lumen axis and the delivery lumen axis extendingin a side-by-side manner along a first segment of the proximal portionand defining a first geometric axis plane; the proximal portion of thecatheter body sidewall having a cross-sectional shape comprising atleast one substantially flat major side that extends along at least asegment of the proximal portion of the catheter body in a plane that istransverse to the first geometric axis plane to cause the proximalportion of the catheter body to preferentially bend as the catheter bodytracks a contour of the heart, the catheter body preferentially bendingin a direction that the delivery lumen exit port is oriented, thecatheter body sidewall comprising a curved inner wall forming a guidebend just proximal to the delivery lumen exit port to bias the deliverylumen exit port away from the guide lumen and toward the heart duringadvancement through the pathway to facilitate passage of the fixationmechanism of the cardiac lead through a vessel wall into the myocardium;wherein the first segment is a distal segment of the proximal portionextending to the delivery lumen exit port; the delivery lumen axis andthe guide lumen axis extending in a side-by-side manner along a secondsegment of the proximal portion, the second segment proximal to thefirst segment; the delivery lumen axis and the guide lumen axisextending along the second segment defining a second geometric axisplane transverse to the first geometric axis plane.